A group of physicists working with data from a particle detector at the Tevatron collider announced last month that they had found something they could not explain. High-speed smash-ups between protons and their antimatter counterparts, observed by the Illinois site's CDF detector, appeared to yield a certain kind of package in unexpected abundance: a massive particle known as the W boson along with two jets of other particles. The CDF excess hinted at the existence of some unknown particle, an unidentified and possibly disruptive addition to the family of particles described by the long-reigning, exceptionally well-tested Standard Model of particle physics.
That hint has now gotten stronger with the addition of new Tevatron data, according to a conference talk (pdf—the relevant section begins on page 31) by CDF team member Giovanni Punzi of the National Institute of Nuclear Physics in Pisa, Italy. Punzi said that the evidence for new physics was now closer to the five-standard-deviation (5-sigma) threshold for confidence in a finding that physicists use as the gold standard for a new discovery. (At the time of the April announcement CDF only had enough data to support a 3.2-sigma claim.) Now, independent confirmation from DZero, the other detector at the Tevatron, or from the European Large Hadron Collider would greatly strengthen the case for a new particle.
In a post on Discover's Cosmic Variance blog, Caltech theoretical physicist Sean M. Carroll nicely contextualized the tantalizing but still unconfirmed finding:
If this is real—still a very, very, big if—it's the beginning of the "beyond the Standard Model era" in collider particle physics. Things aren't going to snap into place overnight; there will be false starts, mysteries, and sudden epiphanies. That's where the real fun is in science.
Photo of the CDF detector: Fermilab